The debut of these two lenses timed themselves at a time which we witnessed some
brilliance of Canon EF lenses being introduced at almost the same time (such as the
Canon
EF 70-200mm f/2.8L USM) but the lens that caught the entire community
in 1995 was the first zoom lens that incorporated with an innovative Image stabilizer
technology. Rather surprisingly, Canon has chosen its immensely popular 75-300mm
as its first trial. The resulting product, Canon EF 75-300mm f/4~5.6 II IS USM as
it was called, stole the limelight among the new releases and thus, there are actually
three versions of the Canon EF 75-300 tele-zoom lens in the EF lens family at this
period.

Physically, it weighs heavier at 650g
and can be easily differentiated from other Canon EF 75-300mm zoom lenses with an
IS metal plate mounted onto the center section of the lens barrel. The zoom ring
is narrower and the gold USM ring mark is moved to front section of the filter attachment
ring. The center section has a control for adjustment or activation of IS function.
It was hailed as the world's first interchangeable
lens for SLR cameras that incorporates with a built-in an Image Stabilizer to counter
camera-shake or more accurately, blur correction effect equals to an increase of
two steps of shutter speed. The inclusion of this feature greatly expands the working
range of handheld photography where typically associated blur image deliveries with
slow speed film under low ambient light or other difficult conditions. Optically,
in terms of elements and lens group, the lens is differed from other EF 75-300mm
tele-zooms, but actually there are redesigned as six lens groups, of which the second
group is for IS activation. Level of camera shake is detected by vibration detecting
gyro sensors. In addition, a micro USM (Ultrasonic Motor) in the drive system ensures
silent AF.

Introduction: What is the principle
of camera shake which results in blurred pictures? 1. I guess no photographer can
hold the camera perfectly still. 2. Whenever the camera moves with the shutter open,
the image on the film moves too. 3. The film records the entire process of movement
while the shutter is open, so the photograph is blurred. How to avoid camera shake
and blurred pictures? The rule of thumb to equalize these issue for decades by photographers
are usually use a tripod to hold the camera steady or sense the shutter speed drops
to a level not comfortable to hold and shoot steadily; use a fast shutter speed to
minimize the recording time of the film or simply use a flash. Each of these methods
have its advantages and the other way round. Tripods aren't easily portable, and
can't be used in some situations; High-speed shutters can't be used in even slightly
dimmer locations and flashes aren't allowed in many places, useless with distant
subjects and usually gives a flat impression.

So, theoretically If a camera has a built-in
function that compensates for the camera shake, you can be sure you'll have fewer
blurred pictures. This idea became the concept behind development of a telephoto
zoom lens with a built-in image stabilizer function to counter camera/lens shake.
The Canon Image Stabilizer System actually has been used on video camcorders and
binoculars has now been adapted for the EF lens. The result is the development of
a new line, the IS lens (Image Stabilizer lens), distinguishing Canon from competing
lens manufactures. Indirectly, development effort has also resulting in the emergence
of a new class of EF lenses and realization of an IS functions within the lens has
broaden the range of handheld photography. Naturally, telephoto and telephoto zoom
lenses (esp. those with a slow starting aperture) will be the best lens group to
incorporate this feature. The well-received Canon 75-300mm was chosen as the first
Canon EF lens to try out consumer response to evaluate its marketing potential in
1995.

The main feature of the IS-powered lenses are:- 1. IS functions broaden the range
of handheld photography as it enables to set up to 2 steps faster shutter speed.
2. IS effectiveness can be verified through the viewfinder. Press the shutter button
halfway to activate the IS function, and verify the compensation for camera shake
through the viewfinder. 3. Reliable optical quality and AF capability with Micro
USM. First, it is a 4x telephoto zoom lens with built-in Micro USM; next, it is a
design that represents substance and high quality.

TECHNICAL APPEAL

1. Canon image stabilizer technology. The "shift method" image stabilizer
technology used on the EF75-300 f/4-5.6 USM lens was developed for use on interchangeable
lenses for the SLR camera. It operates on a different image-stabilization principle
than the Vari-Angle Prism (VAP) method used on video camcorders and anti-vibration
binoculars. a. Shift method (EF75-300 f/4-5.6 IS USM) Feature: Provides satisfactory
image quality for still images. b. Vari-Angle Prism method (Video camcorders, anti-vibration
binoculars) and makes it highly adaptable to a wide variety of products. A question
may raised here:- WHY uses the shift method ? Canon answered that since the front
lens element of a EF lens is usually larger than that of a comparing video or binoculars,
using a VAP system would require development of a very wide diameter VAP. Instead,
the shift method stabilizes the image by shifting the group two lenses inside the
lens, which have already a relatively smaller effective diameter, making it possible
to minimizes the increase in SIZE from earlier lens models. The resulting Canon EF
75-300mm f/4.0~5.6 II IS USM is not anything larger in dimension than the standard
version(S) of 75-300 except the center part of the lens barrel is slight broader
than normal.

2. The Principle of the Image Stabilizer Whenever the camera vibrates due
to hand shake or other causes while the shutter is open, the light passing through
the lens also vibrates, and the results are recorded on the film as a blurred image.
The image stabilization system built into the EF75-300 f/4-5.6 IS USM lens causes
a portion of the lens groups (compensative optical system) to move in parallel with
the external movement, refracting the light rays in a direction that neutralizes
the camera movement and holds the light rays steady as they reach the film surface.
The result stabilizes the image. (see illustrations below):-

3. Image Stabilizer Control The image stabilizer starts to operate when the
shutter button is pressed halfway. When hand shake is detected by gyro sensors, a
signal is sent to drive the compensative optical system, which is controlled by the
first high-speed 16-bit microcomputer to be used on any EF lens. The Canon EF 75-300
IS USM lens was the worlds first interchangeable lens for SLR cameras.

However, there was also a Nikon compact
Zoom 700VR (Zoom 105VR) lens on the market, and is the world's first lens shutter
camera to feature Vibration Reduction function (released in April 1994). The following
is a comparison of the two models (Highlighted numbers are Canon):- Focal length/Aperture:
75-300mm/4-5.6 / 38-105mm/4-7.8; Image stabilizing system Shift type (2nd group lenses) Shift type (3nd group lenses); Maximum correctable
angle: ±0.70/ ±0.60; Verification of stabilization
image through viewfinder:- Available / Not available; Operating noise from image stabilization
operation:- Quiet / Noise from reduction gears; Type: Interchangeable lenses / Lens shutter camera SLR cameras

The result makes it an excellent
tele-zoom lens for PORTRAITS and OUTDOOR SPORTS . When use on digital cameras with
focal multiplier of 1.6 (i.e, 5D, 20D, Rebel XT/350D, 10D, 300D, D1, D30, D60), the
Image Stabilizer 300mm is equivalent to a 480mm on a film camera (like a cropped
effect on astandard 35mm film, hehe..).

Designed exclusively for Canon EOS
cameras; this world's first interchangeable lens with a built-in Image Stabilizer
(IS) dramatically reduces the chance of a blurred photograph due to camera motion
("shake") especially when shooting at long focal lengths with slow shutter
speed. Controlled by a built-in 16-bit microcomputer, a series of gyro sensors and
micro-motors instantly shift one of the lens groups to compensate for inadvertent
camera motion. A very practical benefit of the IS system is a reduction in the old
"focal length = shutter speed" rule by 2 F-STOPS. for an example, you can
expect sharp pictures at 200 mm with a shutter speed of only 1/60th sec. greatly
enhances possibilities.

Below are extracts from a Q&A session
on questions relating to effective application of IS in an optical lens for 35mm
photography:-

Q: Is the image stabilizer effective
even for moving subjects? A: When tracking a fast-moving subject (planes, cars,
etc.), hunting might occur. Such panning shots will take practice.

Q: Can the image stabilizer be used while taking pictures on a moving boat, plane,
car, train, etc.? A: If the camera shake is not too severe, it can be corrected.

Q: When can't the image stabilizer be
used? A: Turn off the image stabilizer before taking pictures in the following
cases: 1. When using a tripod. (Using the image stabilizer while the camera is mounted
on a tripod will cause the image stabilizer to misoperate.)

2. During bulb exposures. (Using the
image stabilizer during a long exposure may cause the image to shift and blur.)

Q: Are there any other precautions for using the image stabilizer? A: When the
image stabilizer is turned on or off, the image may appear to shake in the viewfinder.
This occurs when image-stabilizing lens group is unlocked and centered. It does not
affect the actual picture. Also with certain EOS cameras, the image in the viewfinder
may appear to shake in the following cases: 1. After a picture is taken. 2. While
the camera's built-in flash recycles. 3. After a picture is taken in the DEP mode.
This momentary image shake does not affect the actual picture. When the self-timer
or EF-M is used with the EOS 55, the image stabilizer cannot be used.

Q: Is there any indication in the viewfinder or on the LCD panel when the image stabilizer
is on? A: Since the image stabilizer operation can be confirmed by looking at
the image in the viewfinder, there is no indication in the viewfinder or on the LCD
panel.
Q: What happens when the image stabilizer is not used? A: The image-stabilizing
lens group is centered and locked in place. The lens then becomes an ordinary 75-300mm
zoom lens.

Q: Why does the image stabilizer still operate for a while even after the shutter
button is released? A: If the shutter button is pressed and released repeatedly
within a short period of time, it would be inconvenient for the user if the image-stabilizing
lens group locked in place immediately after the shutter button is released each
time.

Q: What is that snapping sound when the,image
stabilizer is turned on and off ? A: It is the sound of the image-stabilizing
lens group's locking mechanism.

Q: Why is it better to take the picture after waiting at least one second after pressing
the shutter button halfway? A: The gyro sensor's output need this much time to
stabilize after the camera is turned on.

Q: What happens if the user cannot wait that long to take the picture after pressing
the shutter button halfway? A: Although the picture can be taken, the image stabilizer's
maximum effect may not be obtained.

Q: When the image stabilizer is operating, there is a slight vibration. Does it affect
the picture? A: The slight vibration is due to the image-stabilizing lens group's
high-speed control operation. It does not affect the picture.

Q: When the lens is shaken, there is a rattling sound. Does this pose any problem?
A: This is to prevent the image-stabilizing lens group from sticking. It does
not degrade the optical performance.

Q: When Custom Function No. 4 is on, how does the image stabilizer turn on? A:
Pressing the AE lock button turns on the image stabilizer. With the EOS 55, pressing
the shutter button halfway turns on the image stabilizer as usual and pressing the
AE lock button activates the autofocus only.
Q: How different is this lens' image stabilizer from Nikon's Zoom 700VR image stabilizer?
A: The Nikon also has an image-stabilizing lens group and gyro sensor. However, the
Nikon uses a coreless motor to drive the image-stabilizing lens group while the Canon
lens uses a moving coil to drive the lens group directly. Also, the Nikon's telephoto
focal length is 105mm. Since Canon lens' telephoto length is 300mm, the image stabilizer
control is more precise.

Q: How superior is the Canon lens
compared to the Nikon Zoom 700VR? A: Since the image-stabilizing lens group is
driven directly, the response is faster and it can correct camera shake over a wider
frequency range.

Q: What is the camera shake correction range in degrees? A: ±0.7*. (The
Canon 12 x 361S binoculars is 0.9*.)
Q: What power source does the image stabilizer use? A: The camera supplies all
power.
Q: What is the power consumption? A: If the image stabilizer is used for 10 sec.
per picture, the battery life will be about.30 percent less than usual.

Q: What about the optical performance? Also, does the image stabilizer degrade the
optical performance? A: The optical performance is virtually the same as that
of the EF 75-300mm f/4-5.6 11 USM lens. The image stabilizer does not degrade the
optical performance.
Q: When the lens is not being used, must the Image Stabilizer switch be turned off?
A: When the camera is turned off, the image-stabilizing lens group locks. Therefore,
the image Stabilizer switch need not be turned off.

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